blocks|key|3354392|text|我相信，软引用和幻影引用来自Java。一个长而弱的引用(将true传递给C#的WeakReference构造函数)可能被认为类似于Java的PhantomReference。如果在C#中有类似于SoftReference的引用，我不知道它是什么。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3354393|弱引用不会延长对象的生命周期，因此，一旦所有强引用都超出范围，就允许对其进行垃圾回收。它们对于保留初始化成本较高的大型对象很有用，但如果它们不在使用中，则应可用于垃圾回收。|3354394|这对于减少应用程序的内存消耗是否有用，完全取决于应用程序的具体情况。例如，如果您的缓存对象数量适中，将来可能会重用，也可能不会重用，那么弱引用可以帮助改善缓存的内存消耗。然而，如果应用程序使用大量的小对象，弱引用将使问题变得更糟，因为引用对象将占用同样多或更多的内存。|3354395|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

Soft and phantom references come from Java, I believe. A long weak reference (pass true to C#'s WeakReference constructor) might be considered similar to Java's PhantomReference. If there is an analog to SoftReference in C#, I don't know what it is.

Weak references do not extend the lifespan of an object, thus allowing it to be garbage collected once all strong references have gone out of scope. They can be useful for holding on to large objects that are expensive to initialize, but should be available for garbage collection if they are not actively in use. 

Whether or not this will be useful in reducing the memory consumption of your application will depend completely on the specifics of the application. For example, if you have a moderate number of cached objects hanging around that may or may not be reused in the future, weak references could help improve the memory consumption of the caches. However, if the app is working with a very large number of small objects, weak references will make the problem worse since the reference objects will take up as much or more memory.

blocks|key|3141465|text|MSDN对weak+references有一个很好的解释。关键的引语在底部，上面写着：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3141466|3141467|+避免使用弱引用作为+automatic+solution+to+memory+management+problems。相反，应该开发一个有效的缓存策略来处理应用程序的对象。|blockquote|style|BOLD|3141468|3141469|3141470|每次我在野外看到WeakReference时，它都被用作内存管理问题的自动解决方案。对于您的应用程序的问题，可能有更好的解决方案。|3141471|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/ms404247.aspx^0|5|F|0|0|0|1|9|B|S|14|J|0|0|0|0^^$0|@$1|2|3|4|5|6|7|V|8|@]|9|@$A|W|B|X|1|Y]]|C|$]]|$1|D|3|-4|5|6|7|Z|8|@]|9|@]|C|$]]|$1|E|3|F|5|G|7|10|8|@$A|11|B|12|H|I]|$A|13|B|14|H|I]|$A|15|B|16|H|I]]|9|@]|C|$]]|$1|J|3|-4|5|6|7|17|8|@]|9|@]|C|$]]|$1|K|3|-4|5|6|7|18|8|@]|9|@]|C|$]]|$1|L|3|M|5|6|7|19|8|@]|9|@]|C|$]]|$1|N|3|-4|5|6|7|1A|8|@]|9|@]|C|$]]]|O|$P|$5|Q|R|S|C|$T|U]]]]

MSDN has a good explanation of <a href="http://msdn.microsoft.com/en-us/library/ms404247.aspx" rel="noreferrer">weak references</a>. The key quote is at the bottom where it says:

<blockquote>
 Avoid using weak references as an
 automatic solution to memory
 management problems. Instead, develop
 an effective caching policy for
 handling your application's objects.
</blockquote>

Every time I've seen a WeakReference in the wild, it's been used as an automatic solution to memory management problems. There are likely better solutions to your application's problems.

blocks|key|359567|text|在Android+development+tutorial中解释了精彩的WeakReference真实示例。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|359568|视图上有一个图像(位图)和一个图像容器(ImageView)。如果图像不是从内存(而是从磁盘、网络)加载的，那么它可以锁定UI线程和屏幕。为了避免这种情况，可以使用异步任务。|359569|当异步任务完成时，问题就出现了。图像容器在那个时候可能一点用处都没有(屏幕改变或滚动后Android卸载不可见的视图部分)。WeakReference可以在这方面提供帮助，ImageView将被垃圾回收。|359570|class+BitmapWorkerTask+extends+AsyncTask<Integer,+Void,+Bitmap>+{
++++private+final+WeakReference<ImageView>+imageViewReference;

++++public+BitmapWorkerTask(ImageView+imageView)+{
++++++++imageViewReference+=+new+WeakReference<ImageView>(imageView);
++++}
++++//+Method+for+getting+bitmap+is+removed+for+code+clearness

++++//+Once+complete,+see+if+ImageView+is+still+around+and+set+bitmap.
++++@Override
++++protected+void+onPostExecute(Bitmap+bitmap)+{
++++++++if+(imageViewReference+!=+null+&&+bitmap+!=+null)+{
++++++++++++final+ImageView+imageView+=+imageViewReference.get();
++++++++++++if+(imageView+!=+null)+{
++++++++++++++++imageView.setImageBitmap(bitmap);
++++++++++++}
++++++++}
++++}
}|code-block|syntax|javascript|359571|附注:该示例是用Java编写的，但C#开发人员可以理解。|359572|来源：http://developersdev.blogspot.ru/2014/01/weakreference-example.html|359573|entityMap|0|LINK|mutability|MUTABLE|url|http://developer.android.com/training/displaying-bitmaps/process-bitmap.html|1|http://developersdev.blogspot.ru/2014/01/weakreference-example.html^0|1|S|0|0|0|0|0|0|3|1V|1|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@$A|11|B|12|1|13]]|C|$]]|$1|D|3|E|5|6|7|14|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|15|8|@]|9|@]|C|$]]|$1|H|3|I|5|J|7|16|8|@]|9|@]|C|$K|L]]|$1|M|3|N|5|6|7|17|8|@]|9|@]|C|$]]|$1|O|3|P|5|6|7|18|8|@]|9|@$A|19|B|1A|1|1B]]|C|$]]|$1|Q|3|-4|5|6|7|1C|8|@]|9|@]|C|$]]]|R|$S|$5|T|U|V|C|$W|X]]|Y|$5|T|U|V|C|$W|Z]]]]

Brilliant real example with WeakReference is explained in <a href="http://developer.android.com/training/displaying-bitmaps/process-bitmap.html" rel="nofollow noreferrer">Android development tutorial</a>.
There is an image (Bitmap) and image container on the view (ImageView). If image will be loaded not from memory (but e.g. from disk, net) then it can lock UI thread and the screen. To avoid it an async task can be used.
The problem arises when async task finishes. Image container can be not useful at all at that time (screen is changed or Android unloads invisible view part after scrolling). WeakReference can help here and ImageView will be garbage collected.
<pre><code>class BitmapWorkerTask extends AsyncTask&lt;Integer, Void, Bitmap&gt; {
 private final WeakReference&lt;ImageView&gt; imageViewReference;

 public BitmapWorkerTask(ImageView imageView) {
 imageViewReference = new WeakReference&lt;ImageView&gt;(imageView);
 }
 // Method for getting bitmap is removed for code clearness

 // Once complete, see if ImageView is still around and set bitmap.
 @Override
 protected void onPostExecute(Bitmap bitmap) {
 if (imageViewReference != null &amp;&amp; bitmap != null) {
 final ImageView imageView = imageViewReference.get();
 if (imageView != null) {
 imageView.setImageBitmap(bitmap);
 }
 }
 }
}
</code></pre>
P.S. the example is in Java, but can be understood by C# developers. 
Source: <a href="http://developersdev.blogspot.ru/2014/01/weakreference-example.html" rel="nofollow noreferrer">http://developersdev.blogspot.ru/2014/01/weakreference-example.html</a>

Can someone explain the main benefits of different types of references in C#?

<ul>
<li>Weak references</li>
<li>Soft references</li>
<li>Phantom references</li>
<li>Strong references.</li>
</ul>

We have an application that is consuming a lot of memory and we are trying to determine if this is an area to focus on.

Weak reference benefits

内存管理

Android

容器

Java

有人能解释一下C#中不同类型引用的主要好处吗？弱referencesSoft referencesPhantom referencesStrong引用。我们有一个消耗大量内存的应用程序，我们正在尝试确定这是否是一个需要重点关注的领域。

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